Potential alternative approaches to xenotransplantation

• Several technologies compete with xenotransplantation.
• Mechanical devices are largely limited to cardiac support or replacement.
• Pluripotent stem cells may ultimately cure diabetes.
• Regenerative medicine can replace simple structures, but not yet solid organs.
• Blastocyst complementation is unlikely to replace xenotransplantation.

There is an increasing worldwide shortage of organs and cells for transplantation in patients with end-stage organ failure or cellular dysfunction. This shortage could be resolved by the transplantation of organs or cells from pigs into humans. What competing approaches might provide support for the patient with end-stage organ or cell failure? Four main approaches are receiving increasing attention – (i) implantable mechanical devices, although these are currently limited almost entirely to devices aimed at supporting or replacing the heart, (ii) stem cell technology, at present directed mainly to replace absent or failing cells, but which is also fundamental to progress in (iii) tissue engineering and regenerative medicine, in which the ultimate aim is to replace an entire organ. A final novel potential approach is (iv) blastocyst complementation. These potential alternative approaches are briefly reviewed, and comments added on their current status and whether they are now (or will soon become) realistic alternative therapies to xenotransplantation.